Intermittent engine stalling, v 2

In article >,
(Leon van Dommelen) wrote:

> The major grounds are on
> >the head near the former location of the throttle body,
>
> There is a ground strap there? Or just grounded wires?

It's a ring terminal on a thick wire sprouting from the harness. It
mounts to a stud on top of the very front of the head on the intake
side. Right next to the ISC, if you still have one there.

You'd think that one solid system ground would be enough, but it's not.

---
Lanny Chambers
'94C, St. Louis
http://www.hummingbirds.net/alignment.html

Lanny Chambers wrote:
> In article >,
> (Leon van Dommelen) wrote:
>
>
>>The major grounds are on
>>
>>>the head near the former location of the throttle body,
>>
>>There is a ground strap there? Or just grounded wires?
>
>
> It's a ring terminal on a thick wire sprouting from the harness. It
> mounts to a stud on top of the very front of the head on the intake
> side. Right next to the ISC, if you still have one there.
>
> You'd think that one solid system ground would be enough, but it's not.

Once you have voltage drop in the ground line, either as a result of
series resistance or asking it to carry an appreciable amount of current,
it's not a ground any longer.

Grounding is hard. Ask any RF, high-current DC, or modern digital designer.

Dana

(Leon van Dommelen) wrote:

>I think I will take my starter button out of the circuit
>first too. I had problems with the big red button, so why not with the
>KGW?

The starter button is off the list. I apologize for being of so
little trust.

Leon

Gee, I almost spelled that "thrust".

--
Leon van Dommelen Bozo, the White 96 Sebring Miata .)
http://www.dommelen.net/miata
EXIT THE INTERSTATES (Jamie Jensen)

In article >,
(Leon van Dommelen) wrote:

> I apologize for being of so
> little trust.
>
> Gee, I almost spelled that "thrust".

There's probably a more appropriate newsgroup for that sort of thing,
Leon... :-)

---
Lanny Chambers
'94C, St. Louis
http://www.hummingbirds.net/alignment.html

Lanny Chambers > wrote:

>In article >,
> (Leon van Dommelen) wrote:
>
>> The major grounds are on
>> >the head near the former location of the throttle body,
>>
>> There is a ground strap there? Or just grounded wires?
>
>It's a ring terminal on a thick wire sprouting from the harness. It
>mounts to a stud on top of the very front of the head on the intake
>side. Right next to the ISC, if you still have one there.

I cleaned them this morning. They were very clean, though. I did
rearrange another earth that was on it to make the primary connection
somewhat better. But it did not seem that was a likely culprit. I
also cleaned some other connections and made a connection more secure.
None of it seemed a problem, though.

So I started the car and fiddled with all wires and connectors below the
hood that I could see. Nothing produced the slightest hesitation,
though shocks while driving do cause hesitations. So I put the passenger
seat forward and feel the wires coming out of the Link ECU. Bingo.
Instant engine stall.

Presumably, a pin from one of the connectors has come loose. To install
the ECU, we had to take every single pin out of the existing Mazda ECU
connectors and put them in Link connectors, about 50 of them. (Well,
Hector did; if I would have to do it, it would have been a disaster. I
would not have gotten the ECU if I would have recognized the crazy amount
of rewiring needed beforehand.)

Anyway, I cannot find the wire with the problem. The pins seem to be all
in the connectors correctly by visual inspection. I managed to get the
pin of the wire I suspected first out of the connector with a very tiny
electronics screwdriver, but it seems to be perfectly fine. I did not
manage to get the pin of the wire that I suspected second out of the
connector and in any case, that wire does not seem to be the one either
on further examination. Nor could I see a problem.

The bottom line is that I pressed every pin down as far as I could in the
connectors and seem to have made the problem worse. I now have to press
hard on the connectors to prevent the Link ECU from outputting garbage.
So I am wondering whether I am not barking up the wrong tree, and whether
there might be invisible damage of the circuit board or a broken wire.
Of course, if the latter is the case, all hope is lost. There is no
way I am going to find a broken wire among a bundle of 50 of them. Or
replace them all.

Anyway, next in with the multimeter to test 50 pins and hope that they do
not reconnect when the ECU is in a position that I can get at both ends.

Leon

--
Leon van Dommelen Bozo, the White 96 Sebring Miata .)
http://www.dommelen.net/miata
EXIT THE INTERSTATES (Jamie Jensen)

(Leon van Dommelen) wrote:

Update: all the pins had continuity, but the thing was no longer
working at all. Eventually, I discovered that if I put the right
kind of pressure on the circuit board, the thing would come back.

Further research allowed me to restore the car to operational
condition by clamping a plastic screw driver between board and CPU
box in the right place, screwing the box down with just enough
force, and then screwing the box on the rear wall using a washer
between one of the legs to provide just enough torsion. Doing
that actually allowed the wires to be moved quite freely without
stalling the car. Which makes it pretty clear that the problem
is the ECU, and not the connectors or wires after all.

Fortunately, it appears that Flyin Miata has some sort of capability
of diagnosing the boards and repairing bad solders or whatever.
If not, I guess it is either another $1,500 ECU, presumably much more
than the market value of the car, or trying to continue with a plastic
screwdriver-clamped torsion-boxed ECU.

The latter worked quite well for doing early weekend shopping before
taking out the ECU to mail to FM. So I am wondering how long a
screw-drivered, torsion boxed Link ECU might last? Anybody wants to
offer any guesses? I am worrying vibration may deteriorate it further
over time.

Leon

--
Leon van Dommelen Bozo, the White 96 Sebring Miata .)
http://www.dommelen.net/miata
EXIT THE INTERSTATES (Jamie Jensen)

In article >,
(Leon van Dommelen) wrote:

> So I am wondering how long a screw-drivered, torsion boxed Link ECU
> might last? Anybody wants to offer any guesses?

How long does it take to get to the farthest point in your weekend plans
from your house? Mr. Murphy has your answer.

I predict your dreams will be haunted by the ghost of your ME101
professor...

---
Lanny Chambers
'94C, St. Louis
http://www.hummingbirds.net/alignment.html

I think i sean a used EC on Ebay this week 25.00 look under ebay auto's and
then go to the parts and then I do Mazda Miata and thats how i look for my
parts
"Leon van Dommelen" > wrote in message
news
>
> I have been having intermittent stalling of the engine for a long time
> now.
> At fairly random times the engine completely cuts out for a brief moment
> after which it picks up again normally. This is typically immediately
> followed by one or two similar stumbles, and then problemless driving.
>
> It happens at fairly random times, though it is much more likely to occur
> just after I have started driving, and it seems to have some correlation
> with
> significant road roughness. On the other hand, I might have been driving
> for
> many hours, and then suddenly on a beautifully smooth asphalt road, it
> cuts
> out, out of the blue sky, so to speak.
>
> Water in the fuel seemed to be a plausible cause, but I put several
> bottles of Heet and similar through, and it stayed. In addition, after
> half a year or so, a fuel tank removal and cleaning, and about 5,000
> miles, it is hard to see how the water could still stick around. So
> I am now thinking ignition.
>
> Yesterday afternoon, while driving normally on a two lane highway, for the
> first time the engine did not want to recover, and it did not want to
> restart
> on the side of the road. I probably flooded it; clouds of blue smoke came
> out
> of the tail pipe cranking it, despite the fact that there was no sign of
> ignition. Also, I noticed a strong smell of fuel, so fuel was obviously
> being
> delivered.
>
> Anyway, after an hour wait and some cranking with the fuel fuse out, it
> still
> did not want to start, and I had it towed to a shop. Needless to say,
> when
> the shop tried next morning it started and ran fine, after the flooded
> fuel
> was gone, so the problem could not be determined.
>
> So it seems that the problem is the ignition cutting out, rather than the
> fuel delivery. Unfortunately, the thing is irreproducible for
> examination,
> so as far as I see, the only thing to do is to start replacing parts
> until it goes away. (Correction, but I already know the other thing to do
> is write down the telephone numbers of the local towers; the AAA took two
> hours to arrive, after the thunderstorm had come and gone.)
>
> The question is: any suggestions on which parts to replace first? What
> parts are likely to develop problems on a 134k Miata that has seen some
> very rough treatment?
>
> Leon
>
> --
> Leon van Dommelen Bozo, the White 96 Sebring Miata .)
> http://www.dommelen.net/miata
> EXIT THE INTERSTATES (Jamie Jensen)

"Dale" > wrote:

>I think i sean a used EC on Ebay this week 25.00 look under ebay auto's and
>then go to the parts and then I do Mazda Miata and thats how i look for my
>parts

Thanks, but my ECU connectors are rewired and only a Link will fit.

Nobody in their right mind is going to put all those pins back into stock
connectors. I know I am not.

Leon

--
Leon van Dommelen Bozo, the White 96 Sebring Miata .)
http://www.dommelen.net/miata
EXIT THE INTERSTATES (Jamie Jensen)

(Leon van Dommelen) wrote:

>Fortunately, it appears that Flyin Miata has some sort of capability
>of diagnosing the boards and repairing bad solders or whatever.

Well, the power supply solders on the board had come loose. $35 or so
fixed it. Everything seems to be OK again. I used some foam while
mounting the repaired board to reduce the possibility of vibration.

Leon

>If not, I guess it is either another $1,500 ECU, presumably much more
>than the market value of the car, or trying to continue with a plastic
>screwdriver-clamped torsion-boxed ECU.
--
Leon van Dommelen Bozo, the White 96 Sebring Miata .)
http://www.dommelen.net/miata
EXIT THE INTERSTATES (Jamie Jensen)